Displays as devices of information displaying are one of the key elements of information and communication systems, including television systems. The increase of bandwidth, or informational capacity of such systems is an actual task. Its solution is provided both by increasing the number of parallel channels (relative to displays—the number of elements or pixels in the display screen), and by increasing speed of information transmission (relative to the display—increasing the display frame rate).
Taking into account the relationship of both factors in the systems with a given bandwidth, one can vary every of them at the expense of another. Relative to displays, however, the frame rate should always be above a certain critical frequency, at which the screen shows flicker-free images. For many applications, such as in cinema and television, the critical frame rate of 24-50 Hz is allowed, while according to medical recommendations, and taking into account the observation of fast moving objects (like a flying ball) on a display screen the frequency of 90-100 frames per second is more preferable (for Russia the value 100 fr./sec is better agreed with the frequency of the electric net). It is better to retain this value and for displays with sequential change of colors (in time), promising the triple reduction of the number of display elements and observing whole (non-structured) and more bright image due to the elimination of the triad of color filters. In such a case, the refresh rate on the display screen should be of 270-300 Hz, and using the technology of three-dimensional stereovision—even twice more.
Really the most widespread display technologies currently provide a much lower frame rate that is explained by slow processes of active or passive light modulation respectively in emitting or electro-optical material of a display screen. For example, in cathode-ray television displays the frame rate can be up to 300 Hz, in displays based on organic light-emitting materials—potentially up to several hundred Hz, but actually (because of the high currents) is electronically limited to 200 Hz, in plasma displays the frame rate also does not exceed 200 Hz, and in the most widespread displays based on nematic liquid crystals (NLC), the maximum frame rate is only 120-160 Hz.
Concerning to the number of pixels (spatial resolution), in advanced video projectors and television displays the preferred format is the so-called “High-Definition>> (HD)—1920×1080 pixels. In personal computers the format 1024×768 (XGA) prevails till now, and screens of smart devices (primarily the screens of mobile phones) still remain 800×600 pixels (SVGA) and even a 640×480 (VGA). However, due to the constant need in increasing the throughput of information and communication systems, especially in conditions of the limited speed of displays, the general trend is the steady increase of their spatial resolution. Not only the formats XGA (about 1000×1000 or 1K×1K pixels) and HD (of the order 2000×1000 or 2K×1K pixels) are master, but also (2K×2K) and even (4K×2K) pixels [1].
Increasing the number of pixels, however, leads to serious technological problems and difficulties in addressing the display elements. Though modern methods of data processing and pixel addressing allow to address parallelly several parts of the frame and selective addressing only changed pixels in a frame, nevertheless the task of increasing the number of pixels on the screen is associated with great difficulties. Solving the problem by using the high-resolution common composite screen composed of a few display screens, i.e. due to spatially and frequency agreed screens makes a composed display cumbersome, difficulty controlled and expensive, and therefore not effective.
Thus, the throughput of information displaying on a screen of contemporary display is restricted both in the speed, and spatial resolution.
High resolution is especially needed in displays destinated for projecting the information onto a large screen (including TV screen). Information is projected onto a screen via an optical assembly comprising a light source and projection optics. The video projectors based on a micro display with a micro mirror or liquid crystal matrix addressed by drivers, made on silicon integrated technology are most widespread [2].
In all types of video projectors a white light source is often used, such as a compact high-pressure lamp, and the colors are selected by using filters or polarization prisms. In recent years, LEDs with RGB or white light, and even more advanced laser diodes [4] begun to be used for reading the images, but a very significant problem arises: to create two important components for laser video projectors—the effective laser diodes of green radiation and the compact non-mechanical type despecklers to suppress interference noise.
In known video projector DLP (from Digital Light Processing) of Texas Instruments Inc. [2], in the matrix of micro mirrors, each mirror of size 15×15 micrometers is fixed on two hinges, and it can be quickly (electromechanically, for about ten microseconds) deflected at angles +10 or −10 degrees under the pulses of an electric voltage generated by means of silicon integrated circuits. As a result, the light reflected from the mirror passes or does not pass through the diaphragm, so the intensity of the output optical signal has only two values: 1 or 0. Halftones (gray levels) needed to produce color images are formed in such a “digital” micro display electronically—by varying the frequency of deflection of each individual mirror. This reduces the speed of the micro display and frame rate of the video projector. However, taking into account both parameters—rapidity and spatial resolution, such DLP projector has a very high informativeness: the frame rate of the 768×768 matrix of micro mirrors with a capacity of 3 color bits in the three-chip high-speed video projector (with three micro displays and reading the information by different RGB light sources) reaches 4750 Hz, while for 8 and 15 color bits—1780 and 950 Hz, respectively. Due to the high speed of such a micro display operation the color images can be formed even by one micro display instead of three, if to input different color components (RGB) for reading alternately.
The matrix of micro mirrors is able to reflect the light intensity effectively that allows the use DLP video projector for image displaying on a large collective screen, including the cinema screen. However, the projector has a limited term (about 3 years) of continuous reliable operation because of the mechanical principle of micro mirror deflection; besides, its disadvantage is the high value of the control voltage −30 V that requires the specialized integrated circuits for this micro display control.
Projection displays are known [2, 3], in which in every of three different (RGB) color channels of the video projector a micro display with NLC operates, which is made using LCoS (Liquid Crystal on Silicon) technology. For example, helmet-mounted video projectors are widespread, and in recent years—compact pico projectors, used individually or combined with other smart devices and mobile phones, and able to display on a screen with a size of about 1 sq. meter the images of VGA and SVGA formats with the brightness of 15-20 lumens. Limitation of screen size and image format is due to low brightness of used light sources. Because of the use of nematic liquid crystals the speed of these devices is also limited. Although some types of microdisplays based on NLC are intended for a specific type of high resolution video projectors and have a format 4K, in general, due to the low speed of NLC the micro displays and based on them video projectors are not highly informative.
The closest to the proposed invention (a prototype) is a video projector [4] for a projection display comprising a LC micro display based on the structure FLCoS (Ferroelectric Liquid Crystal on Silicon) and an optical unit of reading the information formed in the structure. This unit consists of a light source and projection optics, optically coupled to the structure FLCoS and the screen onto which the information is projected. As a material in the FLCoS-structure the helix ferroelectric LC of smectic type is used (FLC), and the light sources in three different RGB color channels are LEDs of red, green and blue radiation.
Unlike to NLC, where electro-optical response time does not depend on the sign of the electric field (due to the quadratic dependence on the field), and the initial state of NLC layer slowly (for milliseconds in the best case) returns after electric voltage switching off under the force caused by the elastic deformation of NLC layer, in FLC the electro-optical effect is linear on the electric field, i.e. FLC responds to the sign of applied voltage. As the result the electro-optical response time at switching on and switching off, when bipolar control voltage pulses are applied, is the same and is given by [5]:τ˜γφ/(Ps·E),  (1)where γφ—FLC rotational viscosity, Ps—value of the vector of spontaneous polarization, E—electric field tension. In practice response times ON and OFF, depending on the amplitude of control bipolar pulses (from a few to tens of volts) are from hundreds to tens of microseconds, i.e. shorter on the order—two orders than in NLC. Because of this the first letter F in the abbreviation FLCoS is often translated as “fast”.
In the described prototype [4] the electro-optical effect by Clark-Lagerwall is used in FLC in the structure FLCoS of a micro display. This effect is implemented in thin (1-2 micrometers) FLC layers and is characterized by bistable modulation characteristic due to the strong interaction of a layer with boundary surfaces [6]. Therefore bistable FLC-display cells of this type are also called “surface-stabilized structures”, and micro displays based on them—“digital” (they have two optical states, like in micro mirror DLP). The frequency of light modulation in such structures can be up to several kHz at the control electric voltage of ±2, 5 . . . 10 V.
To generate a halftone (gray scale) and hence colors in the company Displaytech like in DLP a decision was suggested to modulate the light with different frequency [2-4]. Through this approach, Displaytech created a whole range of addressable (by means of a silicon control matrix) color “digital” micro displays with a large number of elements (over one million) and small aperture (diagonal is less than an inch), competing with based on NLC micro displays and exceeding their speed of image refreshing (240 frames/sec). This speed already allows to provide sequential (alternative) formation of color instead of the spatial one (using the triad filters) and more comfortable observation of 3D information.
However described known video projector does not solve the problem of a substantial increasing the frame rate and spatial resolution, i.e. improving its informative content to a value at least equal, if not greater, than in DLP video projector.
Thus, the known video projector for the projection display comprising LC micro display on the base of the structure FLCoS with FLC and an optical unit of reading the information formed in FLCoS-structure, consisting of RGB LED light source (with LEDs of red, green and blue radiation) and the projection optics, optically coupled with FLCoS-structure and a screen on which the information is projected, provides a sufficiently high (up to 240 Hz) frame rate and spatial resolution of 106 . . . 107 pixels, however,                frame rate of the video projector is limited because of the impossibility to implement physically continuous modulation characteristics with high modulation frequency in a micro display based on FLCoS-structure with used bistable FLC;        for the same reason to have the grayscale modulation characteristics the complicated pulse frequency addressing of micro display elements is used that reduces the frequency of refreshing images (frames) proportionally to the increasing the number of gray scale levels (in bits);        as a result of these limitations, the sequential color change (in time) and changing the frame for the left and right eyes during the formation of color stereoscopic image simultaneously are feasible only at low frequency (about 40 Hz in the best case) of frames observed by each eye, and therefore, their perception is uncomfortable, taking into account that the frequency of comfortable perception (without flicker and image blur) is 90-100 Hz;        amount of hues of colors (color gamut) determined by the spectral purity of RGB components of readout radiation is limited by using LEDs, the spectral width of which is several tens of nanometers, i.e. more than 10 times exceeds the spectral width of laser diodes;        brightness of the readout light beam is limited by the power density of LEDs radiation to some small solid angle, and it is 10 times less than the power density to the same solid angle which is inherent for the laser diode.        
The tasks solved in the proposed video projector are:                increasing the frame rate almost twice—up to 540-600 Hz, and comfortable perception of 3D stereoscopic images at sequential color change in time in a single micro display with the structure FLCoS due to the use in this structure of the new high-speed helix-free FLC with a halftone modulation characteristic;        expanding the color gamut and increasing the image brightness due to readout the information formed in the micro display with FLCoS-structure by means of using RGB laser beams alternately illuminating micro display in each frame;        destruction of the ability of the laser beam reading out the information to the interference, and thereby suppressing the interference speckle-noise in images formed by this beam, due to input to the video projector the electrically controlled device—a despeckler that is the one-channel phase-modulating FLC-cell;        providing on a screen real time displaying the information blocks (images) with the capacity of 108 . . . 109 pixels and with different geometric configuration by means of input into an optical channel of the video projector a two-dimensional scanner, such as electromechanical (galvanometer) mirror scanner, implementing a spatial scan of the output beam.        
The invention is illustrated by the following description with reference to the drawings.